1. Field of the Invention
The present invention relates to a high-efficiency encoder for encoding a video signal with a screen aspect ratio of 4:3 and a video signal with an aspect ratio which is greater than 4:3 (for example, 16:9).
2. Description of the Prior Art
Generally, a video signal including extremely large quantity of information, and in recording or transmitting the signal, the quantity of information is reduced by high-efficiency coding (bit rate reduction coding) so that picture quality deterioration may not be visually obvious. For example, an input video signal is blocked and transformed orthogonally, and coded by quantizing or variable length coding so that the coded data quantity may be constant (the constant coding data quantity being x) in every specified number of orthogonal transformation blocks (assume m blocks).
Such conventional constitution, however, is not sufficiently flexible enough to be capable of encoding signals with different aspect ratios such as, for example, a signal with an aspect ratio of 4:3 and a signal with the aspect ratio of 16:9. Usually, the signal with the aspect ratio of 16:9 is wider in frequency band width than the signal with the aspect ratio of 4:3, and hence the input data quantity is greater. Therefore, in the conventional constitution, when a signals with an aspect ratio 16:9 and a signal with an aspect ratio 4:3 are both controlled and coded so that the orthogonal transformation data of m blocks may be the constant coding data quantity x, the coding data quantity per unit time differs between the two type signals.